TWI574054B - Manufacturing method of mirror having at least two mirrors, mirror of projection exposure apparatus for lithography, and projection exposure apparatus - Google Patents

Description

Manufacturing method of mirror having at least two mirrors, mirror of projection exposure apparatus for lithography, and projection exposure apparatus

The present invention relates to a method of fabricating a mirror having at least two mirror surfaces. Further, the present invention relates to a mirror for a projection exposure apparatus for lithography and a projection exposure apparatus including the same.

Projection exposure devices for lithography are typically divided into illumination systems as well as projection objectives. The illumination system produces a desired light distribution for illuminating the pattern of a mask or reticle. With the projection objective, the illuminated pattern is imaged onto a light-sensitive material with a very high resolution, and the photosensitive material is thereby exposed in a pattern-structured manner. The actual structure is fabricated in the semiconductor material based on the pattern of exposure in the photosensitive material, for example using subsequent working steps.

Both the illumination system and the projection objective have generally a variety of optical components, such as lenses and/or mirrors. For projection exposure devices designed for operation at very short wavelengths (eg wavelengths less than 100 nm), the use of mirrors is necessary because it is not possible to obtain materials that are sufficiently high and sufficiently uniformly transported, so that it is not possible to manufacture enough Quality lens. In the wavelength range below about 100 nm, it is also called "extreme ultraviolet", abbreviated as EUV. A lithography system operating in the EUV range is typically designed for an operating wavelength of 13.6 nm. However, other operating wavelengths may be used depending on the availability of the light source and optical components.

In order to allow the pattern to be exposed to the photosensitive material with high precision, the mirrors used in the projection exposure apparatus must be manufactured with high precision and orientated with respect to each other. In addition, care must be taken to ensure that the deviation of the mirror's precise shaping and precise orientation during the operation of the projection exposure apparatus is only within tolerances. For these reasons, in many cases, the mirror has an extremely strong substrate body to impart a high mechanical stability to the mirror. However, due to the robust embodiment of the mirror and the large external dimensions involved, problems in the structural space occur, especially in the basic optical design of the projection exposure apparatus requiring two mirrors to be back-to-back with a small distance from each other. When configured.

In this context, DE 10 2005 042 005 A1 discloses a large aperture projection objective for obscured pupils for lithography, revealing that a mirror is embodied as a double mirror, two of which are respectively mirrored It is disposed on the front side and the rear side of the substrate.

However, the misalignment between the two mirrors caused by the conventional manufacturing and measurement methods for manufacturing the dual mirrors requires the use of the remaining mirrors or other optical components of the projection objective due to the associated imaging aberrations. Perform a full correction. This can cause problems in particular when the number of optical components present is relatively small and the possibility of correction is therefore very limited.

Another problem is that in the known method of measuring the misalignment between two optical surfaces (for example, the two optical surfaces of the lens), the measurement is generally performed through the substrate body. Therefore, in order to accurately measure the result, the substrate body must be established. Strict requirements. For lenses, this generally does not incur additional expense because the light used for exposure also passes through the substrate body, and the lens must have high optical quality for this reason. In contrast, for mirrors whose imaging properties are characterized by their surface rather than by the bulk nature of their substrate body, the substrate body suitable for accurate measurement during transport will incur considerable additional costs, in addition Layer restrictions are also placed on suitable materials.

SUMMARY OF THE INVENTION One object of the present invention is to provide a mirror for a projection exposure apparatus for lithography that avoids problems with the construction space and that can be accurately exposed to the photosensitive material by the projection exposure apparatus.

This object is achieved by a method of manufacturing a mirror and a mirror according to the scope of the independent patent application.

The mirror of the projection exposure apparatus for structuring exposure of a photosensitive material according to the present invention has a substrate body, a first mirror surface, and a second mirror surface. The first mirror surface is formed on a first side of the substrate body. The second mirror surface is formed on a second side of the substrate body, the second side being different from the first side of the substrate body. The substrate system is fabricated from a glass ceramic material.

The mirror according to the invention has the advantage that it can be embodied in an extremely compact manner, so that a relatively small construction space is required in the projection exposure apparatus. Another advantage is that a glass ceramic material having a very low coefficient of thermal expansion can be used so that the shape and position of the mirror can remain virtually constant even if the temperature changes.

The invention further relates to a mirror for a projection exposure apparatus for lithographic exposure of a structured exposure of a photosensitive material; the mirror has a substrate body, a first mirror surface and a second mirror surface; the first mirror surface is formed on the substrate body The first mirror is formed on a second side of the substrate body; the second side is different from the first side of the substrate body, and the substrate body has a volume within the substrate body Changed to a refractive index of at least 1 ppm. This indication of the change in refractive index is related to the wavelength of 633 nm, which is typically used as the measurement wavelength in interferometric measurements.

Mirrors embodied in this manner have the advantage that a variety of suitable materials are available for use in embodying the substrate body, and thus the desired properties of the substrate body can be achieved with selected materials.

The refractive index of the substrate body can vary, in particular, by at least 10 ppm within the volume of the substrate body. The indication of the change in refractive index is again related to the wavelength of 633 nm.

Furthermore, the present invention relates to a mirror for a projection exposure apparatus for lithographic exposure of a structured exposure of a photosensitive material; the mirror has a substrate body, a first mirror surface and a second mirror surface; the first mirror surface is formed on the substrate a second mirror surface formed on a second side of the substrate body, the second side being different from the first side of the substrate body; and the mirror having at least one reflective auxiliary surface ( Reflective auxiliary surface). The mirror according to the invention preferably has at least three auxiliary surfaces.

A mirror having at least one reflective auxiliary surface has the advantage that the position of the first mirror and the position of the second mirror can be determined very accurately at a lower cost.

The mirror can be embodied such that the auxiliary surface reflects light that does not contribute to the exposure of the photosensitive material. In particular, the auxiliary surface can specifically reflect light that does not contribute to exposure of the photosensitive material. This has the advantage that the auxiliary surface can be optimized for measurement purposes in a manner that does not accommodate exposure requirements.

The auxiliary surface may be embodied in a spherical shape at least in several regions. This simplifies the possible measurements that include the auxiliary surface.

Furthermore, the auxiliary surface can be embodied as a reference, the desired position of the first mirror and the desired position of the second mirror being predifined relative to this reference. Likewise, the desired position of the second mirror relative to the first mirror surface can be predefined. In this way, the specification of the mirror can be specified with high accuracy.

The first mirror surface and/or the second mirror surface have an actual position that differs from the desired position by a displacement distance of at most 100 nm and an angle of rotation of at most 100 nrad. The actual position of the first mirror surface and/or the second mirror surface can also be different from the desired position by a displacement distance of 10 nm (especially a maximum of 1 nm) and a maximum value of 10 nrad (especially the maximum value is 1 nrad) rotation angle. Embodying such mirrors with high accuracy has the advantage that the possible remaining positional deviation can easily be compensated for by the remaining components of the projection exposure apparatus or without compensation at all.

The mirror can be embodied such that the first mirror surface and the second mirror surface reflect light that is sensitive to exposing the photosensitive material and having a wavelength of less than 100 nm.

The mirror can have exactly two mirrors. However, the mirror can also have three or more mirrors.

The first side of the substrate body can be embodied as a front side, and the second side of the substrate body can be embodied as a rear side facing away from the front side.

For a normal incidence exposure light, the first mirror surface and the second mirror surface may each have a reflectivity of at least 20%, preferably at least 50%.

Furthermore, the first mirror surface and the second mirror surface may be separated from each other by a region having a reflectance of less than 20% for normally incident exposure light.

The first mirror surface may have a first partial region, and the second mirror surface may have a second partial region, the mirrors being embodied such that any light beam reflected in the first partial region is not The reflected beams in the second partial region intersect. This means that the first mirror surface and the second mirror surface are spatially separated from each other.

The first mirror surface and/or the second mirror surface may have a curvature.

The mirror may be further embodied to reflect light that is exposed to the photosensitive material after being reflected by the first specular surface and reflected at least twice in front of the second mirror.

The invention further relates to a projection exposure apparatus for lithographic exposure of a structured exposure of a photosensitive material, wherein the projection exposure apparatus has at least one mirror according to the invention.

The invention further relates to a method of fabricating a mirror having a substrate body, a first mirror surface and a second mirror surface. In the method according to the invention, the first mirror surface and the second mirror surface are interferometrically measured with respect to their position relative to each other, and in this procedure, light is directed directly onto the first mirror surface, And directing light to the second mirror surface via an additional mirror.

The method according to the invention has the advantage that at least two mirror faces can be realized which are oriented very precisely with respect to one another in a small installation space. In this case, it is particularly advantageous that the light does not have to pass through the substrate body during the measurement, and therefore the optical properties of the substrate body are not critical to the measurement. Therefore, during the manufacture of the mirror, for the substrate body, a material that allows measurement of its optical properties through the substrate body can be used, and the measurement of its optical properties does not require high accuracy (especially, it is not required) The accuracy required to use the mirror in a lithographic projection exposure apparatus). Another advantage is that the first mirror surface and the second mirror surface can be measured without changing the measuring arrangement. In this case, the first mirror surface and the second mirror surface can even be measured simultaneously. In particular, the first mirror surface and the second mirror surface can be manufactured with a positional offset relative to each other, the position being predefined by an optical design, which corresponds to a displacement maximum of 100 nm, in particular a maximum of 10 nm or even The maximum value is 1 nm and the combined rotation maximum is 100 nrad, especially the maximum is 10 nrad or even the maximum is 1 nrad.

The mirror can be embodied to be used in a wavelength range below 100 nm (especially at a wavelength of 13.6 nm), wherein the first mirror surface and/or the second mirror surface can have at least a reflectance for normal incidence in this wavelength range. 20%, preferably at least 50%.

The processing of the first mirror surface and/or the second mirror surface can be performed according to the measurement results of the first mirror surface and the second mirror surface. In this way, the desired accuracy of the mirror can be reliably achieved. In this case, an allowance can first be employed to avoid excessive material removal. If the desired position of the two mirrors has been reached, only uniform removal is achieved until the mirror positions are at a desired distance from each other. However, it is also possible to utilize an applied material to reduce or eliminate excessive material removal. This can be achieved, for example, by growing material from a vapor phase.

Light may be focused onto the first mirror surface and/or the second mirror surface during the first mirror surface and the second mirror surface measurement. In this way, the position of the detected position can be determined with great precision. In addition, during the measurement of the first mirror surface and the second mirror surface, light may be guided to the first mirror surface and/or the second mirror surface by normal incidence. This allows the form of the first and/or second mirror to be measured with great precision. Using a combination of focus and normal incidence measurements, the shape and spatial arrangement of the mirrors can be determined with extreme precision.

The first mirror surface can be measured using a first set of diffractive structures, and the second mirror surface can be measured using a second set of diffraction structures. The diffraction structures can each be embodied, for example, as a computer generated hologram, or CGH for short. For measuring surfaces embodied in virtually any desired form, it may be desirable to manufacture CGH with high precision.

The first set of diffractive structures and the second set of diffractive structures can be arranged in defined positions relative to each other. In particular, the relative position of the first set of diffractive structures and the second set of diffractive structures relative to each other can be known with an accuracy better than 10 nm or 1 nm. For example, for lithographic masks, the positional accuracy of this microstructure is also pursued.

For example, the first set of diffractive structures and the second set of diffractive structures can be disposed together on a common carrier. This has the advantage that the orientation of the diffractive structures relative to one another can be permanently maintained even if the position of the diffractive structures is altered by the change in position of the carrier.

The first set of diffractive structures and the second set of diffractive structures can also be distributed between the two carriers, in particular between the two carriers. In addition, a separate carrier may be provided for the first set of diffraction structures and the second set of diffraction structures, respectively.

The measurement of the first mirror and the measurement of the second mirror can be performed in the same position of the mirror. Thereby, the decision of the renewed adjustment or the renewed position associated with the mirror repositioning can be avoided.

For example, a first diffractive structure can be utilized to direct light onto the first mirror surface and a second diffractive structure can be used to direct light onto the additional mirror.

The additional mirror can be measured with respect to its position relative to the second mirror. This prevents the measurement from being adversely affected by the possible offset of the additional mirror from a predefined location. The position of the additional mirror can also be monitored during the measurement of the mirrors of the mirror. The diffractive structures required for this purpose can each be accommodated on the same carrier, which also has a diffractive structure for measuring the mirrors of the mirror.

In a variant of the method according to the invention, in order to measure the second mirror, light is guided through the cutout of the mirror. This process allows for extremely compact measurement configurations.

In another variation of the method according to the invention, in order to measure the second mirror, light in the vicinity of the mirror is guided. This process is applicable in a variety of situations, especially where a mirror without a slit is included.

The invention is explained in detail below based on exemplary embodiments illustrated in the figures.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing an exemplary embodiment of a projection exposure apparatus for lithography according to the present invention. The projection exposure apparatus has an illumination system 1 and a projection objective 2. In the illustrated exemplary embodiment, the projection exposure apparatus is embodied as a catotric system and thus has a dedicated mirror without a lens as an optical element.

The illumination system 1 has a light source 3, a mirror M1, a mirror M2, a mirror M3, and a mirror M4. In the illustrated exemplary embodiment, each mirror of the illumination system 1 has a substrate body and a mirror surface embodied on the substrate body, that is, the mirror M1 has a substrate body B1 and a mirror surface S1, and the mirror M2 has a substrate. The main body B2 and the mirror surface S2, the mirror M3 has a substrate body B3 and a mirror surface S3, and the mirror M4 has a substrate body B4 and a mirror surface S4.

The substrate bodies B1, B2, B3, B4 may be composed of a material having a small coefficient of thermal expansion, such as a glass ceramic material such as Zerodur or ULE. In addition, for example, tantalum or silicon carbide is also suitable as a mirror material. The materials of the substrate bodies B1, B2, B3, and B4 may have a high degree of inhomogeneity in refractive index. In particular, within the volume of the substrate bodies B1, B2, B3, B4, the refractive index of each substrate body can vary by at least 1 ppm (parts per million), or by at least 10 ppm. These indications of the change in refractive index in the body of each substrate are related to the wavelength of 633 nm, which is typically used as the measurement wavelength in interferometry. The mirrors S1, S2, S3, S4 can be formed, for example, by a layer stack, in particular by alternating layer stacks of tantalum and molybdenum composing.

In particular, the mirror M1 can be embodied as a collector mirror having a concave mirror surface S1. The mirrors M2 and M3 may have faceted mirror surfaces S2 and S3. In particular, the mirror M4 can be embodied as a focusing mirror with a concave mirror surface S4.

Light source 3 is embodied, for example, as a plasma source and produces light having an EUV range of wavelengths less than 100 nm. For example, the wavelength of light produced by source 3 can be 13.6 nm or 7 nm.

The light generated by the light source 3 is sequentially reflected by the mirror surface S1 of the mirror M1, the mirror surface S2 of the mirror M2, the mirror surface S3 of the mirror M3, and the mirror surface S4 of the mirror M4, and then irradiated onto the mask 4. In this case, the illumination system 1 can be designed not to illuminate the entire area of the reticle 4, but only to illuminate a partial area, which may have, for example, a ring shape or a ring shape.

The photomask 4 has a pattern that reflects the illumination light so as to face the projection objective lens 2. The pattern of the photomask 4 may represent, for example, constituent parts of the integrated circuit. In Fig. 1, only the projection objective 2 is illustrated as "Black Box". The construction of the projection objective will be described in detail with reference to FIG. 2.

The projection objective 2 images the pattern of the reticle 4 on the photosensitive material used to coat the wafer 5. Therefore, the wafer 5 is disposed in the beam path downstream of the projection objective 2. Imaging the pattern onto the photosensitive material of the wafer 5 can be achieved, in particular, in the context of a scanning procedure in which only a partial area of the pattern to be imaged is illuminated, and the reticle 4 and the wafer 5 are relative to the projection objective 2 Synchronous movement. In order to perform the movement in synchronization with the imaging, the imaging scale of the projection objective 2 will be considered in the forward movement of the reticle 4 and the wafer 5. The advancement movement of the mask 4 and the wafer 5 is achieved parallel to the y-direction shown in FIG. The z-direction extends perpendicular to a plane in which the surface of the reticle 4 is disposed and a plane of the surface of the wafer 5.

Figure 2 shows in a schematic view an exemplary embodiment of a projection objective 2 according to the invention.

The projection objective lens 2 has a mirror M5, a mirror M6, a mirror M7, a mirror M8, and a mirror M9, which are successively arranged in a beam path starting from the reticle 4. The mirror M5 has a substrate body B5 and a substantially planar mirror surface S5. The mirror M6 has a substrate body B6 and a concave mirror surface S6. The mirror M7 has a substrate body B7, a convex mirror surface S7, and a concave mirror surface S7'. The mirror M7 thus has two mirror faces S7 and S7' on its substrate body B7, which are embodied on opposite sides of the substrate body B7. The mirror M8 has a substrate body B8 and a concave mirror surface S8, and the mirror M9 has a substrate body B9 and a convex mirror surface S9.

Therefore, light is sequentially reflected on the mirror surface S5 of the mirror M5, the mirror surface S6 of the mirror M6, the mirror surface S7 of the mirror M7, the mirror surface S8 of the mirror M8, and the mirror in the path from the mask 4 to the wafer 5. The mirror surface S9 of the M9 and the mirror surface S7' of the mirror M7.

In the illustrated exemplary embodiment, all of the mirrors S5, S6, S7, S7', S8 and S9 are rotationally symmetric with respect to the optical axis 6 of the projection objective 2 and may have a spherical or aspherical shape. However, it is not actually necessary for the complete slewing body to appear in each mirror. Rather, for the mirrors S5, S6, S7, S7', S8, and S9, substantially only the light formed on the photosensitive material that is used to expose the wafer 5 is irradiated onto the mirror faces S5, S6, S7, S7', S8. And S9 is enough. Each of the mirror faces S5, S6, S7, S7', S8, and S9 is not formed in a place where light blocking occurs. Otherwise, manufacturing engineering considerations and considerations regarding the operation of the projection objective 2 are employed in the best possible manner as a decision to actually form the swivel positions of the mirrors S5, S6, S7, S7', S8 and S9 and do not form these The standard of the position of the mirror.

Instead of the rotationally symmetric mirrors S5, S6, S7, S7', S8 and S9, it is also possible to use mirrors S5, S6, S7, S7', S8 and S9 which have no rotational symmetry and are called "free form surfaces". . The above description of the mirrors S5, S6, S7, S7', S8 and S9 in a rotationally symmetrical form, plus the necessary changes, applies in a similar manner to freeform surfaces. Furthermore, the explanations about the mirror faces S5, S6, S7, S7', S8 and S9 of the projection objective 2 are also applied in a similar manner to the mirrors S1, S2, S3, and S4 of the illumination system. In particular, the illumination system 1 can also have a mirror with two mirrors on the common substrate body.

In order to obtain high image quality during imaging of the pattern of the reticle 4 onto the photosensitive material of the wafer 5, the formation of the mirror faces S5, S6, S7, S7', S8 and S9 of the projection objective lens 2 must be manufactured with high precision. And the position of these mirrors relative to each other must be adjusted with high precision. However, after the mirror M7 is manufactured, the mirror faces S7 and S7' are reflected on the substrate body B7 because they are combined, so that it is impossible to perform adjustment independently of each other. Only two mirrors S7, S7' can be adjusted jointly. This means that it is no longer possible to correct the misalignment of the two mirror faces S7 and S7' with respect to each other. It is only possible to try to correct the aberration caused by the misdirection by using the adjustment operations of the remaining mirrors S5, S6, S8 and S9. But this can be tricky. Furthermore, the relatively small number of mirrors S5, S6, S8 and S9 will limit the likelihood of correction, resulting in generally only partial correction of aberrations due to misalignment between mirrors S7 and S7'.

In order to at least alleviate this problem, measures will be taken in the context of the present invention to minimize the misalignment between the mirrors S7 and S7' or, more generally, the two mirrors on the common substrate body B of the mirror M. The wrong direction between S and S' is minimized. According to the invention, this can be achieved by performing an interferometric measurement comprising two mirror faces S, S' and, depending on the measurement result, performing a subsequent processing of the mirror M to reduce the misalignment between the two mirror faces S, S'.

This process seems impossible at first, because for the mirrors S, S', it is not possible to use an interferometric method known for lenses, in which the corresponding front side optical surface is optically detected directly, and Optical detection of the corresponding rear side optical surface through the lens. This is because this would require measurement, for example, through the mirror S and the substrate body B. Since it cannot be transmitted in the EUV range, this measurement can be performed at a longer wavelength where the mirror surface S and the substrate body B are sufficiently transparent, but then the substrate body B fails due to lack of optical homogeneity.

Therefore, in the context of the present invention, different processes are employed. Thus, in accordance with a variation of the invention, an auxiliary surface is provided on the mirror M and an auxiliary surface is included in the measurement. This will be explained in detail below with reference to FIGS. 3 to 5.

In another variation, as illustrated in Figures 6 and 7, and particularly for use in the measurement of obscured mirrors, the surface of the constituent parts of the mirror M that are not to be measured is included in the measurement.

In the variation shown in Fig. 8, any of the above additional surfaces is not required when measuring the mirrors S, S'.

Figure 3 shows in schematic view an exemplary embodiment of a mirror M embodied in accordance with the present invention. The mirror M has a substrate body B and two mirror faces S and S', which are embodied on both sides of the substrate body B facing away from each other. For the sake of clarity, the side of the substrate body B on which the mirror surface S is embodied is hereinafter referred to as "front side VS", and the side of the substrate body B on which the mirror surface S' is formed is referred to as "back side RS".

The mirror M as a whole has a basic shape of a cylinder in which the substrate body B has the front side VS of the mirror surface S and the rear side RS of the substrate body B having the mirror surface S' forms the bottom and the top of the cylinder. The three auxiliary surfaces HF1, HF2, and HF3, which are formed in a spherical shape, are disposed on the substrate body B so as to be distributed around the circumference of the side surface of the cylinder. The auxiliary surfaces HF1, HF2, HF3 are very precisely shaped and embodied in the form of reflections. In this case, for the method according to the invention, which is described in detail below, the most important is the precision of the formation (ie the smallest possible offset from the spherical shape) rather than the absolute size (ie the spherical radius). In particular, the auxiliary surfaces HF1, HF2, HF3 can be made of the same material of the mirrors S and S' and thus can have similar reflective properties.

In view of a suitable embodiment of the mirrors S and S', the mirror M shown in Fig. 3 can be used, for example, as the mirror M7 of the projection objective 2 shown in Fig. 2.

The measurement of the mirror faces S and S' of the mirror M (including the auxiliary surfaces HF1, HF2, HF3) will be explained with reference to Figs.

Figure 4 shows, in a schematic view, an exemplary embodiment for measuring the measurement configuration of mirror M when the first measurement step is performed. The measurement is performed in the following manner by means of an interferometer IF embodied as, for example, a Fizeau interferometer:

A parallel beam 7 is produced using a measuring light source 6 embodied, for example, as a laser. The parallel beam 7 is illuminated onto a lens 8 which focuses the beam 7 onto a spatial filter 9. Instead of the lens 8, an objective lens that focuses the beam 7 can also be provided. The spatial filter 9 is embodied, for example, as a small aperture and produces a bundle of divergent beams 10 having a spherical wave front. A spatial filter 9 embodied in a different manner can also be used instead of a small hole. The divergent beam 10 passes through a beam splitter 11 and is then irradiated onto a collimator lens 12. The collimating lens 12 produces a parallel beam 13 having a plane wavefront from the diverging beam 10. The parallel beam 13 passes through a wedge-shaped plate 14 and then emerges perpendicularly through the plane 15 from the wedge plate 14.

The plane 15 is embodied as a partial transmission, thus reflecting some of the parallel beams 13 back to the parallel beams themselves. The reflected beam again passes through the wedge plate 14, is focused by the collimating lens 12, and is then deflected by the beam splitter 11 in the direction of the spatial filter 16. After passing through the spatial filter 16, the reflected beam is illuminated onto a camera objective 17, and then illuminated onto a spatial resolving detector 18, for example, which can be embodied as a CCD wafer. An evaluation electronics 19 is coupled to the spatial resolution detector 18.

The light beam emerging from the plane 15 of the wedge plate 14 is illuminated on the CGH configuration 20. The CGH configuration 20 has a plurality of diffractive structures (not illustrated), particularly a computer generated hologram, abbreviated CGH, which is disposed on a common carrier and produces a series of test beams. The measurement light 21 generated by the CGH configuration 20 is directed onto the auxiliary surfaces HF1, HF2, HF3 of the mirror M. The measurement light 21 is incident on the auxiliary surfaces HF1, HF2, HF3 of the mirror M with normal incidence and is thus reflected back to the measurement light itself. In addition, the CGH configuration 20 produces a metering light 22 that is vertically illuminated on the mirror surface S of the front side VS of the mirror M and reflected back to the metering light itself. Finally, the CGH configuration 20 produces a spotlight 23 that is focused onto the mirror S of the front side VS of the mirror M and reflected back from the mirror S back to the CGH configuration 20.

All of the reflected measurement light passes through the CGH configuration 20, the wedge plate 14 and the collimating lens 12, and is then deflected by the beam splitter 11 to the spatial filter 16. After passing through the spatial filter 16 and the camera objective lens 17, the reflected measurement light is incident on the spatial resolution detector 18, wherein the reflected measurement light and the reflected light beam on the plane 15 of the wedge plate 14 are respectively As a reference beam, the phase interferes. In this manner, a series of interferograms are generated, each detected by spatial resolution detector 18 and analyzed by evaluation electronics 19.

The interferogram generated by the metering light 21 can be used to determine the exact position of the auxiliary surfaces HF1, HF2, HF3. The auxiliary surfaces HF1, HF2, HF3 are embodied in a spherical shape with high precision. Therefore, the surface shape of the auxiliary surface and thus its influence on the measurement light 21 can be known very accurately. Since the reflection of the measurement light 21 on the auxiliary surfaces HF1, HF2, HF3 depends on the surface shape and position of the auxiliary surfaces HF1, HF2, HF3, the auxiliary surfaces HF1, HF2 can be determined from the interference pattern generated by the measurement light 21. The location of the HF3. Thus, for example, the auxiliary surfaces HF1, HF2, HF3 can be configured with high precision at predefined locations, however, these predefined positions must be compatible with the predefined limits of the rigid connections of the auxiliary surfaces HF1, HF2, HF3. . In this way, the position of the entire mirror M is defined with high precision. The preliminary prepositioning of the auxiliary surfaces HF1, HF2, HF3 can be achieved tactilely or in some other way. Even in the case where the auxiliary surfaces HF1, HF2, HF3 are not precisely positioned in a predefined position, their actual position and hence the actual position of the mirror M can be known with high accuracy.

After determining the precise orientation or position of the mirror M as described above, the shape and position of the mirror surface S are measured by means of the measurement lights 22 and 23. For this purpose, an interferogram generated by the interference of the measured light 22 and 23 reflected from the mirror S with the light beam reflected from the plane 15 of the wedge plate 14 is evaluated. From the interferogram of the reflected light 22, the shape deviation of the mirror S from the shape desired in the CGH configuration 20 can be determined in a manner known per se. However, this decision is still unclear since it produces the same result for similar surfaces, i.e., produces the same result by transforming into surfaces of each other by increasing along the normal direction of the surface. Therefore, the measurement light 23 is additionally evaluated. From the interferogram of the reflected light 23, the degree of defocusing of the measured light 23 on the mirror surface S can be determined in a manner known per se, and thus the illumination area of the mirror S and the CGH configuration 20 are determined. the distance. The distance is determined based on the fact that the CGH configuration 20 focuses the metering 23 in a defined manner, that is, the position of the focus relative to the CGH configuration 20 is already known exactly.

Since the measurement of the mirror surface S of the front side VS of the mirror M is performed using the same CGH configuration 20 as with the measurement of the auxiliary surfaces HF1, HF2, HF3, the coordinates defined with respect to the auxiliary surfaces HF1, HF2, HF3 can be measured in the manner described above. The mirror S of the system.

After measuring the mirror S, the CGH configuration 20 is replaced by a CGH configuration 20 having a diffractive structure to measure the mirror surface S' and the detection auxiliary surfaces HF1, HF2, HF3. Furthermore, the mirror M is positioned such that the mirror S' faces the CGH arrangement 20. This can be achieved, for example, by rotating the mirror M by 180° about an axis extending parallel to the surface of the CGH arrangement 20. The measurement of the mirror surface S' of the mirror M relocated in this manner will be explained with reference to FIG.

It is also possible to use the same CGH configuration 20 to perform the measurement of the mirror S and the measurement of the mirror S'. In this example, the CGH configuration 20 has a diffraction structure for measuring the mirror surface S and a diffraction structure for measuring the mirror surface S', and care should be taken to ensure that the diffraction structure required to illuminate each measurement condition must be illuminated. This can be achieved, for example, by partial masking out the light.

Figure 5 shows in a schematic view the measurement configuration of Figure 4 when performing the second measurement step. In Fig. 5, only the interferometer IF is illustrated as a "black box" because its internal structure is the same as that of Fig. 4. In addition to the interferometer IF, the CGH configuration 20 and the mirror M to be measured are also illustrated in FIG. During the second measurement step shown in Figure 5, the same measurement configuration as Figure 4 is actually maintained. Compared to the first measuring step shown in Figure 4, only the orientation of the mirror M relative to the CGH configuration 20 is altered so that the back side RS of the mirror M can be measured. Moreover, depending on the particular embodiment variations, the CGH configuration 20 is replaced, if appropriate, with a CGH configuration 20 having other diffractive structures, or care is taken to ensure that other diffractive structures of the CGH configuration 20 are necessarily illuminated.

In the same manner as the first measuring step, in the second measuring step, the mirror S is first oriented with high accuracy using the auxiliary surfaces HF1, HF2, HF3, or the actual surfaces of the auxiliary surfaces HF1, HF2, HF3 are determined with high accuracy. The position, and thus the actual position of the mirror M, is also determined. Therefore, the same coordinate system that is also used in the first measurement step can be used for the second measurement step.

Next, the mirror surface S' is measured in a manner similar to that achieved by the mirror S in the first measurement step. After the second measurement step is performed, the shape of the mirror surface S and the shape of the mirror surface S' are known with high precision. Further, the positions of the mirror surface S and the mirror surface S' with respect to the auxiliary surfaces HF1, HF2, HF3 are known with high precision, and thus the positions of the mirror surfaces with respect to each other are also known.

As already explained, during the two measuring steps, the precise positioning of the auxiliary surfaces HF1, HF2, HF3 can be dispensed with in each step, as long as the position is determined. However, in this example, in determining the position of the mirror faces S and S' relative to each other, it is necessary to consider the positional offset of the auxiliary surfaces HF1, HF2, HF3 between the first measuring step and the second measuring step, respectively.

In the context of the manufacture of the mirror M, testing and rework are performed using known processing techniques (such as grinding, polishing, etc.), as appropriate, using the above-described measurement methods or measurement method variations or other changes described below. Or the coating surface S, S' formed by the coating method at least once. The originally known processing techniques can be used during redoing.

The measurement and redo mirror M are repeated until the shapes of the mirrors S, S' and the positions of the mirrors S or S' relative to each other are at most different from the desired shape and the desired position. To achieve this, the mirrors S, S' whose shapes are not within tolerances are redone. The positional shift between the two mirrors S, S' can be corrected by the following: subsequent processing of the mirror S, subsequent processing of the mirror S', or subsequent processing of the two mirrors S, S'. Selecting the mirrors S, S' to be redone to correct the positional offset can be combined with the need to correct the shape offset. For example, the mirror S or S' that must be redone to correct the shape offset anyway is used to correct the positional offset. Similarly, it is possible to try to limit the redo for the positional offset to the range of subsequent processing required for the corresponding mirror S, S' for correcting the shape offset. This process is particularly suitable when the two mirrors S, S' must be redone to correct the shape offset and must decide how the positional offset correction should be assigned between the two mirrors S, S'.

In order to avoid removing too much material, as this will not be saved or can only be saved with a high degree of complexity, the tolerance can be used first. If the desired shape and position of the two mirrors S, S' have been reached, only uniform removal is achieved until the mirror positions are at a desired distance from one another. However, coating materials can also be utilized to reduce or eliminate excessive material removal. This can be achieved, for example, by growing material from a vapor phase.

In the manner described, the mirror M can be produced in such a way that the mirrors S, S' each have a shape embodied in a highly precise form and are oriented with respect to each other with high precision, wherein the orientation with respect to each other not only covers the angular orientation, It also covers the distance between each other. In particular, the mirror M can be manufactured with the precision that the mirror M uses in the projection exposure apparatus.

A mirror having three or more mirrors can also be fabricated in a similar manner.

The accuracy of the mirror S and the mirror S' with respect to the shape can be expressed as an offset between the actual shape and the desired shape, respectively. To determine a specific value, the shape offset can be defined as the root mean square value F_RMS, which can be calculated as follows:

In this example, z _i represents the offset of the support point i between the actual value and the desired value. The number of pivot points i is specified as n.

When determining the value F_RMS, care should be taken to ensure that the fulcrum density must be coordinated with the maximum gradient of the shape of the mirror S, S' to give the highest possible value of the value F_RMS. For high gradients, a correspondingly high fulcrum density should be provided.

The allowable tolerance for the shape of the mirror S, S' can be expressed as the upper limit at which the value F_RMS must not be exceeded. As an upper limit of the value F_RMS, for example, values of 1 nm or 0.1 nm can be predefined for the two mirror faces S and S', respectively.

Depending on the needs of the application, the same or different value F_RMS upper limits can be predefined for the two mirrors S and S'.

The value F_RMS specifically contains the effect caused by the offset from the desired shape. The offset from the desired position does not affect the value F_RMS. This difference can be achieved by substituting the desired shape into the actual shape before determining the value F_RMS, and thereby eliminating the influence of the position, that is, using the position as a fit parameter.

The positions of the mirrors S, S' can be defined by three space coordinates and three angles, respectively. Therefore, the positional offset can be described by three difference values and three angular differences, respectively, which can be determined by comparing the desired value with the actual value determined during the substitution of the shape. In this case, the desired value can be predefined with respect to any coordinate system, the coordinate system being defined, for example, by means of the auxiliary surfaces HF1, HF2, HF3. From the corresponding three differences of the space coordinates, the corresponding displacement distance can be calculated, and the corresponding three differences from the angle can be used to calculate the corresponding rotation angles of the positional displacement features. This means that the actual position is shifted to the desired position by a combination of a single displacement of the displacement distance and a single rotation of the rotation angle. In this case, the displacement should be performed along the displacement vector direction because the absolute value of the displacement distance has been determined. The rotation should be performed from the axis of rotation determined by the angular difference in a manner that can be known per se.

In the manner described, the actual position and the positional offset between the desired positions can be detected in a quantized manner for the mirror S and the mirror S', respectively. In particular, since the relative positions of the mirror faces S and S' with respect to each other are important in many cases, it is advantageous to determine the positional shift of the mirror surface S and the mirror surface S' with respect to each other instead of the positional shift of the mirror surface S and the mirror surface. The positional shift of S' or, in addition to the positional shift of the mirror surface S and the positional shift of the mirror surface S', determines the positional shift of the mirror surface S and the mirror surface S' with respect to each other. For example, this can be achieved by selecting a coordinate system such that for one of the mirrors S or S', the actual position matches the desired position. The offset of the actual position of the other mirror S or S' in the same coordinate system corresponds to the relative positional offset. The allowable tolerances for the relative positional shift of the mirrors S and S' can be expressed as the upper limit of the displacement distance and the rotation angle. For example, 100 nm, 10 nm, or 1 nm can be predefined as the upper limit of the displacement distance. For example, 100 mrad, 10 mrad or 1 mrad can be predefined as the upper limit of the angle of rotation. This means that the allowable tolerance for shape offset is generally significantly lower than the allowable tolerance for positional offset.

For example, instead of the displacement distance, the positional offset can also be estimated using the spatial coordinate difference. In a similar manner, the angle difference can be used instead of the angle of rotation. In order to reduce the digital data, in this example, for example, only the maximum value can be evaluated separately. This evaluation can then be carried out using a comparison with an upper limit, which can be of the order of magnitude already mentioned. In this variation, especially the relative positional shift of the mirrors S and S' is also important.

Exemplary embodiments of different configurations of measurement configurations may also be used in the fabrication of mirror M in place of the exemplary embodiments of the measurement configurations illustrated in Figures 4 and 5. This will be explained below with reference to FIGS. 6 to 8.

Figure 6 shows in schematic view another exemplary embodiment of a measurement configuration for measuring a mirror when performing a first measurement step. Similar to FIG. 4, the measurement configuration shown in FIG. 6 has an interferometer IF, a CGH configuration 20, and a mirror M. The difference with respect to the exemplary embodiment of FIG. 4 is the different embodiment of the mirror M and the additional components in the form of additional mirrors 24, which are mounted in the common base 25 together with the mirror M. In contrast to Figure 4, the mirror M according to Figure 6 has no auxiliary surfaces HF1, HF2, HF3. Another difference lies in the fact that the mirror M shown in Fig. 6 has a central slit ZO through which light can pass. Furthermore, Figure 6 illustrates the CGH configuration 20 in an oblique form, which means, for example, that the beam from the interferometer IF and arriving at the interferometer IF does not have to be oriented perpendicular to the CGH configuration 20. Regarding avoiding disturbing reflections, the tilted CGH configuration 20 can be even advantageous. It goes without saying that in the measurement configuration of Figure 6, a non-tilted CGH configuration 20 can also be employed. To show this, the non-tilted CGH configuration 20 is illustrated in Figure 7, which in other respects shows the same measurement configuration.

The measurement light 26 from the CGH configuration 20 is vertically illuminated on the mirror surface S on the front side VS of the mirror M and reflected back to the measurement light 26 itself, that is, the measurement light 26 passes through the CGH configuration 20 and then enters the interferometer IF. The equal amount of light 26 is used to determine the shape of the mirror S.

Furthermore, the measured light 27 is illustrated in Figure 6, which is from the CGH configuration 20, passes through the slit ZO of the mirror M, and then illuminates the additional mirror 24. The additional mirror 24 reflects the measurement light 27 in the direction of the mirror M such that the equal-measurement light is vertically incident on the mirror surface S' on the rear side RS of the mirror M. For this purpose, the additional mirror 24 has a curved surface. The measurement light 27 irradiated on the mirror surface S' on the rear side RS of the mirror M is reflected back to itself, thus causing re-reflection at the additional mirror 24, and then passing through the slit ZO of the mirror M. The metering light 27 then passes through the CGH configuration 20 and enters the interferometer IF. The shape of the mirror surface S' is determined from the measurement light 27 by means of the interferometer IF.

Finally, the third type of photometry 28 is illustrated in Figure 6, which is from the CGH configuration, passes through the slit ZO of the mirror M, and then illuminates the additional mirror 24 with normal incidence and is supplemented by additional mirrors. 24 reflects back to the metering 28 itself. The reflected measurement light 28 reaches the CGH configuration 20 through the slit ZO of the mirror M and then enters the interferometer IF. The shape of the surface of the additional mirror 24 can be determined from the measurement light 28 by means of the interferometer IF. If the shape of the surface of the additional mirror 24 is known with sufficient accuracy, the light 28 is not required to be measured.

In addition to determining the shape of the mirror faces S, S' of the mirror M, the positions of the mirror faces S, S' are also determined. This will be explained with reference to FIG.

Figure 7 shows, in a schematic view, an exemplary embodiment of the measurement configuration of the measuring mirror M when performing the second measuring step shown in Figure 6. In addition to the CGH configuration 20, the components shown correspond to Figure 6. Only the beam path is different from Figure 6. This is achieved with the fact that the CGH configuration 20 has a diffractive structure embodied in a different manner than the measurement configuration of FIG. Another difference lies in the fact that the CGH configuration 20 according to Figure 7 is not tilted. However, similarly, the CGH configuration 20 can also be tilted in FIG.

The measurement light 29 is shown in Fig. 7, which is from the CGH configuration 20 and is focused on the mirror surface S on the front side of the mirror M.

In addition, the measurement light 30 is illustrated, which is from the CGH configuration 20, passes through the slit ZO of the mirror M, and is then reflected by the additional mirror 24 in the direction of the mirror surface S' on the rear side RS of the mirror M, and is focused on the mirror surface S. 'on.

Finally, the measured light 31 is also illustrated in Figure 7, which is from the CGH configuration 20, passes through the slit ZO of the mirror M, and is focused onto the additional mirror 24.

All of the measured light 29, 30, 31 illustrated in Figure 7 can determine the distance between the CGH configuration 20 and the illuminated areas on the respectively detected surfaces, respectively. Together with the information determined in relation to the shape of the detection surface according to Fig. 6, the position of the mirrors S and S' relative to each other on the front side VS and the back side RS of the mirror M can be determined.

The process for the measurement configuration shown in FIGS. 6 and 7 differs from the process according to FIGS. 4 and 5 in that, in the first measurement step, the front side VS and the rear side RS of the mirror are measured in an areal fashion. The two mirrors S, S', and in the second measuring step, the two mirrors S, S' are measured by focusing. For the measurement configuration shown in FIGS. 4 and 5, in the first measurement step, the mirror surface S on the front side VS of the focus measurement mirror M is in the form of a sweep, and in the second measurement step, in the form of a swept surface and focus measurement The mirror surface S' on the side RS of the mirror M.

Instead of the illustrations in Figures 6 and 7, in principle it is also possible to direct the measuring light 27, 30 in the vicinity of the mirror M onto the mirror S' on the rear side RS of the mirror M. This variation is especially useful for mirrors M without a central slit ZO. In this variation, additional mirrors 24 can also be used to cause light to reach all of the points of mirror M.

Furthermore, the first measurement step and the second measurement step can be combined to form a common measurement step, because between the two measurement steps, if the CGH configuration 20 is provided for the first measurement step and the second measurement step Measuring all the required diffraction structures eliminates the need to change the measurement configuration. In this case, in particular, all measurements can also be performed simultaneously.

It is likewise possible to perform a sweeping measurement of the first measuring step and to delete the second measuring step of the focus measurement. In this case, the distance information that can be determined using the second measurement step is obtained in some other way. For example, the distance distance required by the laser distance measuring device can be determined as long as it is allowed for the accuracy requirement.

Figure 8 shows in a schematic view another exemplary embodiment of a measurement configuration for measuring mirror M. The measurement configuration shown in Figure 8 differs in the fact that the diffractive structure of the CGH configuration 20 is disposed on two carriers, that is, the CGH configuration 20 has the assembly 20a and the assembly 20b.

The assembly 20a of the CGH configuration 20 produces a series of measurements 32, 33, 34, 35, 36, 37 from the plane wave, which in the illustration of Fig. 8 is illuminated from the left onto the assembly 20a of the CGH configuration 20. Plane waves can be generated in a similar manner as shown in FIG.

The measured light 32, 33, 34, 35 is reflected at the mirror M and then illuminated on the assembly 20b of the CGH configuration 20. In this case, the measurement light 32 is reflected at the focus, and the measurement light 33 is reflected in the form of a swept surface at the mirror S of the front side VS of the mirror M. The measurement light 34 is reflected at the focus, and the measurement light 35 is reflected in the form of a swept surface at the mirror surface S' of the rear side RS of the mirror M.

The measurement light 36, 37 passes directly (that is, does not reflect at the mirror M) to the assembly 20b of the CGH configuration 20 and is used to determine the distance and thus the positioning of the components 20a and 20b of the CGH configuration 20 relative to one another.

After passing through the assembly 20b of the CGH configuration 20, the measurement light 32, 33, 34, 35, 36, 37 enters the interferometer IF. A reference beam (not illustrated) can be coupled out of a plane wave upstream of component 20a of CGH configuration 20, deflected near CGH configuration 20 and mirror M, and then into interferometer IF. The IF can be constructed in a manner similar to that of FIG. 4, but omitting the beam generating assembly because the beam generating components are configured to abut the component 20b of the CGH configuration 20.

In Fig. 8, the shapes of the mirrors S and S' are also determined using the measured light 33, 35 reflected in the form of a swept surface in a manner similar to the previous exemplary embodiment. The position of the mirrors S and S' relative to each other can be determined by increasing the amount of light 32, 34 reflected at the focus. However, one difference with respect to the previous exemplary embodiment is that the measured light 32, 33, 34, 35 is not vertically or symmetrically illuminated on the mirrors S, S' and thus is not reflected back to itself or mutually from each other .

Therefore, the processing of the mirror M can be performed based on the measurement results in a manner similar to that already described.

1. . . Lighting system

2. . . Projection objective

3. . . light source

4. . . Mask

5. . . Wafer

6. . . Optical axis (Figure 2) / measuring light source (Figure 4)

7,13. . . Parallel beam

8. . . lens

9,16. . . Spatial filter

10. . . Divergent beam

11. . . Splitter

12. . . Collimating lens

14. . . Wedge plate

15. . . flat

17. . . Camera objective

18. . . Spatial resolution detector

19. . . Evaluation electronics

20. . . CGH configuration

20a, 20b. . . CGH configured components

21, 22, 23, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37. . . Measuring light

twenty four. . . Extra mirror

25. . . Shared base

B, B1, B2, B3, B4, B5, B6, B7, B8, B9. . . Substrate body

HF1, HF2, HF3. . . Auxiliary surface

IF. . . Interferometer

M, M1, M2, M3, M4, M5, M6, M7, M8, M9. . . Reflector

RS. . . Back side

S, S', S1, S2, S3, S4, S5, S6, S7, S7', S8, S9. . . Mirror

VS. . . Front side

ZO. . . Central incision

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing an exemplary embodiment of a projection exposure apparatus for lithography according to the present invention.

Fig. 2 shows in schematic view an exemplary embodiment of a projection objective according to the invention.

Figure 3 is a schematic representation of an exemplary embodiment of a mirror embodying the present invention.

Figure 4 shows in schematic view an exemplary embodiment for measuring the measurement configuration of a mirror according to the invention when performing the first measurement step.

Figure 5 shows in a schematic view the measurement configuration of Figure 4 when performing the second measurement step.

Fig. 6 shows in schematic view another exemplary embodiment for measuring the measurement configuration of the mirror according to the invention when the first measuring step is performed.

Figure 7 shows in schematic view the measurement configuration of Figure 6 when performing the second measurement step.

Figure 8 shows in schematic view another exemplary embodiment of a measurement configuration for measuring a mirror.

B. . . Substrate body

HF1, HF2, HF3. . . Auxiliary surface

M. . . Reflector

RS. . . Back side

S, S'. . . Mirror

VS. . . Front side

Claims (19)

A mirror for a projection exposure apparatus for lithography, comprising: a substrate body; a first mirror surface formed on a first side of the substrate body; and a second mirror surface formed on the substrate body a second side, wherein: the second side of the substrate body is different from the first side of the substrate body; the first mirror surface and the second mirror surface are composed of a plurality of multilayer stacks, The reflection is directed for structuring to expose light on a photosensitive material and illuminating the substrate body from outside the substrate body; and the substrate system is fabricated from a glass ceramic material. The mirror of claim 1, wherein for the second mirror, a desired position relative to the first mirror is predefined. The mirror of claim 2, wherein at least one of the first mirror surface and the second mirror surface has an actual position, a displacement distance of up to 100 nm from the desired position and a displacement of at most 100 nrad Rotation angle. The mirror of claim 1, wherein the first mirror surface and the second mirror surface are used to reflect extreme ultraviolet light. The mirror of claim 1, wherein the substrate body has a slit extending from the first mirror surface through the substrate body to the second mirror surface. A mirror for a lithography projection exposure apparatus, comprising: a substrate body having a first mirror surface and a second mirror surface, wherein: the first mirror surface is formed on a first side of the substrate body; The second mirror surface is formed on a second side of the substrate body, the second side is different from the first side of the substrate body; the first mirror surface and the second mirror surface are used for reflection to be guided for the structure Exposing light onto a photosensitive material and illuminating the substrate body from outside the substrate body; and the substrate system is fabricated from a glass ceramic material; and an additional mirror surface forms an auxiliary surface. The mirror of claim 6 wherein the auxiliary surface is positioned to reflect light that does not contribute to the structured exposure of the photosensitive material. The mirror of any of claims 6 and 7, wherein the auxiliary surface is spherical at least in a plurality of regions of the auxiliary surface. The mirror of any one of claims 6 to 7, wherein the auxiliary surface serves as a reference surface, and a first desired position of the first mirror surface and a second desired position of the second mirror surface are opposite to The reference surface is predefined. The mirror of claim 9, wherein at least one of the first mirror surface and the second mirror surface has an actual position that is different from at least one of the first desired position and the second desired position A displacement distance of up to 100 nm and a displacement rotation angle of up to 100 nrad. The mirror of any one of claims 1 to 7, wherein the first side of the substrate body is a front side, and the second side of the substrate body is a back side facing away from the front side. The mirror of any one of claims 1 to 7, wherein the first mirror surface and the second mirror surface each have a reflectivity of at least 20% for a vertically incident exposure light. The mirror of any one of claims 1 to 7, wherein the first mirror surface and the second mirror surface are separated from each other by a region having a reflectance of less than 20% for normally incident exposure light. The mirror of any one of claims 1 to 7, wherein the first mirror mask has a first partial area and the second mirror mask has a second partial area such that it is reflected in the first partial area. Any beam does not intersect the beam reflected in the second partial region. The mirror of any one of claims 1 to 7, wherein at least one of the first mirror surface and the second mirror surface has a curvature. The mirror according to any one of claims 1 to 7, wherein the light guided on the photosensitive material and contributing to exposing the photosensitive material, after being reflected at the first mirror, is irradiated Reflected at least twice before the second mirror surface. The mirror of any one of claims 1 to 7, wherein the substrate body has a refractive index that varies by at least 1 ppm within the volume of the substrate body. The mirror of claim 17, wherein the refractive index of the substrate body varies by at least 10 ppm within the volume of the substrate body. A projection exposure apparatus for lithography, comprising: a light source for generating light; an illumination system for guiding the light on a reticle; and a projection objective for guiding the light on a photosensitive material; wherein the illumination system and the projection objective At least one of the at least one mirror according to any one of claims 1 to 18 of the patent application.